Double-edged Role of KNa Channels in Brain Tuning: Identifying Epileptogenic Network Micro-Macro Disconnection

: Epilepsy is commonly recognized as a disease driven by generalized hyperexcited and hypersynchronous neural activity. Sodium-activated potassium channels (KNa channels), which are encoded by the Slo 2.2 and Slo 2.1 genes, are widely expressed in the central nervous system and considered as “brakes” to adjust neuronal adaptation through regulating action potential threshold or after-hyperpolarization under physiological condition. However, the variants in KNa channels, especially gain-of-function variants, have been found in several childhood epileptic conditions. Most previous studies focused on mapping the epileptic network on the macroscopic scale while ignoring the value of microscopic changes. Notably, paradoxical role of KNa channels working on individual neuron/microcircuit and the macroscopic epileptic expression highlights the importance of understanding epileptogenic network through combining microscopic and macroscopic methods. Here, we first illustrated the molecular and physiological function of KNa channels on preclinical seizure models and patients with epilepsy. Next, we summarized current hypothesis on the potential role of KNa channels during seizures to provide essential insight into what emerged as a micro-macro disconnection at different levels. Additionally, we highlighted the potential utility of KNa channels as therapeutic targets for developing innovative anti-seizure medications.

Identification of New Compounds with Anticonvulsant and Antinociceptive Properties in a Group of 3-substituted (2,5-dioxo-pyrrolidin-1-yl)(phenyl)-Acetamides

We report herein a series of water-soluble analogues of previously described anticonvulsants and their detailed in vivo and in vitro characterization. The majority of these compounds demonstrated broad-spectrum anticonvulsant properties in animal seizure models, including the maximal electroshock (MES) test, the pentylenetetrazole-induced seizure model (scPTZ), and the psychomotor 6 Hz (32 mA) seizure model in mice. Compound 14 showed the most robust anticonvulsant activity (ED50 MES = 49.6 mg/kg, ED50 6 Hz (32 mA) = 31.3 mg/kg, ED50scPTZ = 67.4 mg/kg). Notably, it was also effective in the 6 Hz (44 mA) model of drug-resistant epilepsy (ED50 = 63.2 mg/kg). Apart from favorable anticonvulsant properties, compound 14 revealed a high efficacy against pain responses in the formalin-induced tonic pain, the capsaicin-induced neurogenic pain, as well as in the oxaliplatin-induced neuropathic pain in mice. Moreover, compound 14 showed distinct anti-inflammatory activity in the model of carrageenan-induced aseptic inflammation. The mechanism of action of compound 14 is likely complex and may result from the inhibition of peripheral and central sodium and calcium currents, as well as the TRPV1 receptor antagonism as observed in the in vitro studies. This lead compound also revealed beneficial in vitro ADME-Tox properties and an in vivo pharmacokinetic profile, making it a potential candidate for future preclinical development. Interestingly, the in vitro studies also showed a favorable induction effect of compound 14 on the viability of neuroblastoma SH-SY5Y cells.

Propofol and Sevoflurane Anesthesia in Early Childhood Do Not Influence Seizure Threshold in Adult Rats

Experimental studies have demonstrated that general anesthetics administered during the period of synaptogenesis may induce widespread neurodegeneration, which results in permanent cognitive and behavioral deficits. What remains to be elucidated is the extent of the potential influence of the commonly used hypnotics on comorbidities including epilepsy, which may have resulted from increased neurodegeneration during synaptogenesis. This study aimed to test the hypothesis that neuropathological changes induced by anesthetics during synaptogenesis may lead to changes in the seizure threshold during adulthood. Wistar rat pups were treated with propofol, sevoflurane, or saline on the sixth postnatal day. The long-term effects of prolonged propofol and sevoflurane anesthesia on epileptogenesis were assessed using corneal kindling, pilocarpine-, and pentylenetetrazole-induced seizure models in adult animals. Body weight gain was measured throughout the experiment. No changes in the seizure threshold were observed in the three models. A significant weight gain after exposure to anesthetics during synaptogenesis was observed in the propofol group but not in the sevoflurane group. The results suggest that single prolonged exposure to sevoflurane or propofol during synaptogenesis may have no undesirable effects on epileptogenesis in adulthood.

Fruits for Seizures? A Systematic Review on the Potential Anti- Convulsant Effects of Fruits and its Phytochemicals

: Epilepsy is a devastating neurological disorder. Current anti-convulsant drugs are only effective in about 70% of patients, while the rest remain drug-resistant. Thus, alternative methods have been explored to control seizures in these drug-resistant patients. One such method may be through the utilization of fruit phytochemicals. These phytochemicals have been reported to have beneficial properties such as anti-convulsant, anti-oxidant and anti-inflammatory activities. However, some fruits may also elicit harmful effects. This review aims to summarize and elucidate the anti- or pro- convulsant effects of fruits used in relation to seizures, in hopes to provide a good therapeutic reference to epileptic patients and their carers. Three databases; SCOPUS, ScienceDirect and PubMed were utilized for the literature search. Based on the PRISMA guidelines, a total of 40 articles were selected for critical appraisal in this review. Overall, the extracts and phytochemicals of fruits managed to effectively reduce seizure activities in various preclinical seizure models, acting mainly through the activation of the inhibitory neurotransmission and blocking the excitatory neurotransmission. Only star fruit has been identified as a pro-convulsant fruit, which was attributed to the its caramboxin and oxalate compounds. Future studies should focus more on utilizing these fruits as possible treatment strategies for epilepsy.

NBI-921352, a First-in-Class, NaV1.6 Selective, Sodium Channel Inhibitor That Prevents Seizures in Scn8a Gain-of-Function Mice, and Wild-Type Mice and Rats

NBI-921352 (formerly XEN901) is a novel sodium channel inhibitor designed to specifically target NaV1.6 channels. Such a molecule provides a precision-medicine approach to target SCN8A-related epilepsy syndromes (SCN8A-RES), where gain-of-function (GoF) mutations lead to excess NaV1.6 sodium current, or other indications where NaV1.6 mediated hyper-excitability contributes to disease (Gardella and Moller, 2019; Johannesen et al., 2019; Veeramah et al., 2012). NBI-921352 is a potent inhibitor of NaV1.6 (IC50 0.051 µM), with exquisite selectivity over other sodium channel isoforms (selectivity ratios of 756X for NaV1.1, 134X for NaV1.2, 276X for NaV1.7, and >583X for NaV1.3, NaV1.4, and NaV1.5). NBI-921352 is a state-dependent inhibitor, preferentially inhibiting activated (inactivated or open) channels. The state dependence leads to potent stabilization of inactivation, inhibiting NaV1.6 currents, including resurgent and persistent NaV1.6 currents, while sparing the closed/rested channels. The isoform-selective profile of NBI-921352 led to a robust inhibition of action-potential firing in glutamatergic excitatory pyramidal neurons, while sparing fast-spiking inhibitory interneurons, where NaV1.1 predominates. Oral administration of NBI-921352 prevented electrically induced seizures in a Scn8a GoF mouse, as well as in wild-type mouse and rat seizure models. NBI-921352 was effective in preventing seizures at lower brain and plasma concentrations than commonly prescribed sodium channel inhibitor antiseizure medicines (ASMs) carbamazepine, phenytoin, and lacosamide. NBI-921352 was well tolerated at higher multiples of the effective plasma and brain concentrations than those ASMs. NBI-921352 is entering phase II proof-of-concept trials for the treatment of SCN8A-developmental epileptic encephalopathy (SCN8A-DEE) and adult focal-onset seizures.

Rationale design, synthesis, and pharmacological evaluation of isatin analogues as antiseizure agents

Background: Epilepsy is one of the most common and devastating neurological disease affecting about 1% of the world’s population at any time. Herein, we have reported rationale design and synthesis of 5-acetyl-3-((4-substitutedphenyl)imino)indolin-2-one analogues 3(a-k) as antiseizure agents. Objective: These analogues were designed as four component pharmacophoric model by clubbing structural fragments of potent antiepileptic drugs. Aim of this study was to synthesize structurally designed isatin analogues and screened them for anticonvulsant activity and neurotoxicity. Methods: Designed derivatives were synthesized using bulky scale feasible and inexpensive microwave methodology. All the synthesized compounds were then characterized by multiple spectroscopic techniques and screened for anticonvulsant activity through preclinical in-vivo experiments. Results: The compound 3d have exhibited good anticonvulsant activity in preclinical seizure models with better toxicity profile when compared to standard drugs (3d: ED50 = 31.5 mg/kg, MES test; ED50 = 37.4 mg/kg, scPTZ test; TD50 = 384.3 mg/kg,). Compound 3d have also shown good binding affinity at crucial amino acids of GluN1 subunit of NMDAR (Docking score = -9.30) and fit adequately in the cavity of receptor (Amino acids involved and H-bonding distance = GLY93: acetyl >C=O, 2.38Å; PHE92: acetyl >C=O, 2.22Å; and THR26: >C=O of isatin, 1.71Å). Results of molecular docking supported the structural features present over isatins to persuade potent antiseizure activity. Conclusion: Rationale designing strategy, in-vivo pharmacological profile, and computational studies make us to anticipate the emergence of these molecules as novel antiseizure agents which can be further explored to develop probes for the treatment of epilepsy.

Anticonvulsant Activity of 80% Methanol Leaf Extract and Solvent Fractions of Buddleja polystachya Fresen. (Buddlejaceae) in Mice

Epilepsy is a chronic non-communicable disease characterized by recurrent seizures. According to 2019 WHO report, it affects about 50 million people globally and nearly 80% of them live in low-and middleincome countries. Current antiepileptic drugs have several limitations including lack of response in significant number of patients and intolerable adverse drug reactions. Buddleja polystachya Fresen. (Buddlejaceae) is a medicinal plant used for the treatment of epilepsy in Ethiopian traditional medicine, where the dried leaves are crushed, mixed with local alcoholic beverage and taken orally. Thus, this study was conducted to evaluate the anticonvulsant activity of the 80% methanol leaf extract and solvent fractions of B. polystachya in mice models of seizure. The dried and powdered leaves of B. polystachya were extracted using cold maceration with 80% methanol (1:5 w/v), and the resulting crude extract was fractionated using chloroform and n-butanol to get chloroform, n-butanol and aqueous fractions. Anticonvulsant activities of B. polystachya crude extract and solvent fractions at doses of 100, 200 and 400 mg/kg were evaluated using pentylenetetrazol (PTZ) and maximal electroshock (MES)–induced seizures in mice (n = 6). In addition, motor coordination effects were assessed using rotarod test. Sodium valproate (200 mg/kg), phenytoin (25 mg/kg) and diazepam (5 mg/kg) were used as standards for PTZ, MES and rotarod tests, respectively. Distilled water or 2% tween 80 was used as negative control. All doses of the crude extract exhibited a significant (p < 0.001) anticonvulsant property in both PTZ and MES tests compared with negative control. Similarly, the n-butanol fraction exerted significant (p < 0.001) anticonvulsant effects in both seizure models. However, the chloroform fraction (200 and 400 mg/kg) showed a significant (p < 0.001) anticonvulsant effect in only PTZ-induced seizure model. The aqueous fraction was devoid of any anticonvulsant activity in both models. The crude extract and fractions did not exert any significant changes in motor coordination. Preliminary phytochemical screening of the crude extract and solvent fractions revealed the presence of flavonoids, phenols, tannins, steroids, terpenoids and saponins. In conclusion, the results of this study indicated that the plant has a promising anticonvulsant activity and could be considered as a potential source to develop new anticonvulsant drug.

SYNTHESIS, IN SILICO ANALYSIS AND ANTICONVULSANT ACTIVITY OF NOVEL PYRIMIDINE DERIVATIVES

In this present study, a novel series of chalcones (C1-10) were synthesized by reacting 4-nitro acetophenone and various substituted aromatic aldehydes in an alcohol medium. The title compounds, pyrimidine derivatives (PD1-10), were obtained by the cyclization of chalcones (C1-10) with guanidine carbonate in an alcoholic medium. Each of the newly synthesized compounds was structurally assigned in accordance with FT-IR, 1 H-NMR and mass spectral data. All the synthesized compounds were subjected to in silico analysis among which, some of the synthesized compounds were chosen and evaluated for in vivo anticonvulsant study by employing PTZ-induced seizure and MES seizure models. Compounds PD2 and PD7 demonstrated significant anticonvulsant activity when compared to the standard.